Impregnation of textle materials



Patented Mar. 24, 1936 PATENT OFFICE IMPREGNATION or 'rnx'rm MATERIALS Gustavus J. Esselen, Swampscott, and Walter M. Scott, Wellesley, Mass., assignors to Hooker Electrochemical Company, New York, N. Y., a corporation of New York No Drawing. Application May 26, 1934, Serial No. 727,730

10 Claims.

In co-pending application Serial No. 661,353 there is disclosed a process for impregnating textile materials depending upon the use of a solvent for the impregnating salt that will not of itself cause hydrolysis of the salt and thus dispensing with the necessity for an acid inhibitor to prevent premature hydrolysis; by which process waste of the weighting salt is avoided and damage to the material by the acid inhibitor is eliminated. This result is accomplished through the use of an organic solvent in place of the water heretofore commonly used for the purpose. The I present process is a development of the process aforesaid, in which improved results are obtained by the use of certain solvent mixtures which experience has shown to be particularly well adapted to the purpose intended.

Our invention resides more particularly in the use of certain solvent mixtures including substances of little or no solvent power with respect to the impregnating salts.

One object of our invention is to avoid or reduce weakening of the fibres as a resultof impregnation.

Another object of our invention is to increase the retention, 1. e., the percentage of the weighting metal found in the finished product to that withdrawn from the bath (the difierence, of course, representing waste).

Another object of our invention is to permit the use of cheaper impregnating materials and to overcome the difiiculties inherent in so doing.

Another object of our invention is to reduce the toxicity and fire hazard of the solvent.

A further object of our invention is to reduce loss of solvent by evaporation from the surface of the bath during the weighting operation.

Another object of our invention is to provide a treatment by which the fibres are interlocked or caused to slide less readily over one another, whereby "runs in knitted fabrics are avoided.

Another object of our invention is to increase coverage or opacity of the material.

Still another object of our invention is to reduce the time of immersion of the fabric in the bath and thus increase the output for a given plant investment.

A still further object of our invention is to reduce corrosion of the equipment used in carrying out'the process.

One of the preferred solvents for carrying out the process referred to is methanol, but methanol is relatively expensive and its vapor is more or less toxic, circumstances which render indispensable theuse ofa solvent recovery system.

A less expensive and less toxic solvent would therefore be desirable.

The commercial straight chain paraffine hydrocarbon solvents are inexpensive and low in toxicity, but unsatisfactory solvents for metal 5 salts; however, by mixing them in the right proportions with almost any good solvent for such salts, a solvent mixture may be produced that will be effective, for our purpose.

Among the good solvents for the metal salts 10 that are suitable for our purpose are methanol, toluol, ethylene dichloride, trichlor ethylene, chlorbenzol, etc. Among" the commercial parafiine solvents are petroleum ether, solvent naphtha, Stoddard solvent, etc. The latter is 15 a commercial solvent that has been standardized by the United States Bureau of Standards and designated as Commercial Standard 3-28 or C. S. 3-28.

Methanol is immiscible with these conmiercial 20 paraifine solvents, but any of the other solvents listed above as good solvents may be mixed with any of the above mentioned commercial solvents to form a solvent mixture that will be found suitable for the purposes of our invention. 26 However, these mixtures are not all equally suitable, and while we do not wish to .be limited to any specific solvent, at present one of the preferred good solvents for our purpose is toluol and one of the preferred commercial solvents is 30 C. S. 3-28.

Stoddard solvent," or Commercial Standard 3-28 is defined in Bureau of Standards Bulletin efiective as ofMarch 1, 1928 as a petroleum distillate, clear and free from suspended matter 35 and undissolved water, not darker than 2| Saybolt chromometer, sweet, having a flash point not lower than F., showing an extremely slight discoloration of a clean copper strip after 3.hours at 212 F., evaporating to the extent of not less 40 than 50% when the thermometer reads 350 F.,- having a dry end point not higher than 410 F., showing no acid reaction in the residue and a negative medical test and an absorption of not more than 5% by chemically pure 93.2% sul- 45 phuric acid. This solvent has an initial boiling point of approximately 320 F.

Wherever in the present specification or in the appended claims either of the expressions Stoddard solven Commercial Standard 3-28, 50 U. S. Commercial Standard 3-28 or "C. S. 3-28 occurs, it is to be understood as referring to the solvent defined by the specification just given.

In some cases it may be desirable to add to the mixture a third solvent, such as xylol or butanol. 55

In general, however, we prefer a mixture of C. S. 3-28 and toluol. The proportions may be varied through a wide range, but it is desirable to use as large a proportion of the cheaper C. S. 3-28 as possible and this may be eighty per cent oreven higher.

The resulting solvent mixture is relatively inexpensive, hence after immersion of the fabric it sufiices to recover so much of the solutionas can be squeezed outbetween rolls, without the elaborate provisions otherwise necessary for recovering vapors of the solvent. The toxity and fire hazard of this solvent mixture are so low that no inconvenience results therefrom. Loss of solvent by evaporation from the surface of the bath and the corrosion of the equipment are less than when straight methanol is used as the solvent.

One of the difficulties heretofore generally encountered in the impregnation of textiles is loss of strength in the material. This loss of strength may be attributed to the acid formed by hydrolysis of the weighting salt. To minimize this, we have found it effective to add to the metal salt solution some material having a greasy or unctuous quality which is a non-solvent for the metal chloride used. We have found, for example, that the addition of a small percentage of a fatty acid, such as stearic or oleic acid, to the solvent is effective for the purpose. Another way which we have found of accomplishing a similar result is to use a solvent mixture one constituent of which is a hydrocarbon of relatively poor or low solvent power and high boiling point. That is to say, the constituent of relatively poor or low solvent power provides a protective effect. The explanation of this is probably to be found in the fact that hydrocarbons of the type mentioned, although quite volatile, have an oily component which naturally evaporates last, thus momentarily providing an unctuous protective coating.

After immersing the textile material in a solution of tin or antimony chloride, for example, in one of the above solvents or solvent mixtures, we pass the material through squeeze rolls and dry it in a current of air. It is important that the solvent mixture be completely eliminated, otherwise the subsequent fixation steps are interfered with. For brevity, this removal of the organic liquids will be referred to as drying. For this purpose the drying temperature should be sufficiently elevated, but not excessive, as we find that when the drying temperatures are much above 40 C. there is a tendency toward undue weakening of the fibre. Moreover, when drying temperatures above 25 C. are employed, there is a loss of antimony trichloride by volatilization. After drying, the material is immersed in an aqueous solution of sodium phosphate. The water of the solution hydrolizes the metal chloride. The material is next washed in cold running water to remove any residual acids and dried. This treatment may be repeated until the desired weighting effect has been obtained. The

material is finally immersed in a solution of sodium silicate, washed and dried again.

I Examples Sample No. 1, of silk, was immersed in a methanol solution containing 350 grams of antimony trichloride per liter, passed between squeeze rolls, dried at 10 C., immersed in a 5 per cent solution of cold sodium phosphate, washed, squeezed and dried.

s I Stegric In Loss of strength amp e an crease in N o. solvent grams per weight liter Warp Filling 1 Methanol- 0 112% 46% 47% 2 MethanoL 50 96% 9% This comparison shows very strikingly the protective efiect obtained by adding a minor proportion of stearic acid to the solution.

Sample No. 3, of silk, was immersed in a solution of methanol containing 350 grams of antimony trichloride and 50 grams of stearic acid per liter, passed through squeeze rolls, dried at 25 C., treated with cold sodium phosphate and washed and dried again. After three of these cycles it was passed through a 6 B. solution of sodium silicate at 60 C., squeezed and dried. The increase in weight and retention or percentage of the metal removed from the bath that appeared in the finished product were as follows:

It will be seen that the percentage of retention was 83 or 98 per cent, depending upon whether the antimony is calculated as the oxy-chloride or as the oxide.

The average retention heretofore obtained in weighting with tin by ordinary commercial methods, i. e. out of an aqueous solution, has been approximately 75 per cent. Efforts to weight with antimony out of an aqueous solution have hitherto been thwarted by a loss of more than threequarters of the metal in the hydrolysis or fixation step, giving -a retention of only 26%. The percentage of retention obtained by our process therefore compares very favorably with that of ordinary practice in tin weighting. Our process and that of the co-pending application above referred to, moreover, so nearly eliminates the waste of metal heretofore experienced in antimony weighting that it now becomes for the first time commercially practicableto use this cheap, heavymetal for this purpose, for which it is in many respects ideally suited.

' Sample No. 4, of silk, was immersed for 14 secends in a solution consisting of 80 parts C. S. 3-28 and 20 parts toluol by volume and containing 350 grams of antimony trichloride per liter of solution. The silk was passed through this solution, then through squeeze rolls, and dried for fifteen minutes in a current of air at 25 degrees C.

It was then immersed for five minutes in a cold Sample No. 6 was given a similar treatment, except that the solvent consisted of 80 parts "C. S. 3-28, 10 parts toluol and 10 parts xylol.

The results were as follows:

' Increase in weight after-- Sample One cycle Two cycles Three cycles Silicate bath None of these samples showed any dusting off.

In order to ascertain the resistance to loss of weight in laundering, Samples 4, 5 and 6 were subjected to a test which consisted in boiling them for one-half hour in a 1 per cent solution of olive oil soap, washed and dried, and the loss of weight determined. For purposes of comparison, a piece of silk that had been weighted with tin out of an aqueous solution, by the ordinary commercial process, was subjected to the same test. This is designated as Sample No. 7. The results were as This comparison shows that the process of our invention results in a weighting that is more resistant to the conditions of the laundry than the ordinary commercial weighting process.

Sample No. 8, of silk, was treated as heretofore specified in a solution of methanol containing 350 grams antimony trichloride and 50 grams stearic Sample No. 9 was given a. similar treatment, except that the solventrconsisted of 50 parts C. S. 3-28 and fiopartstoluol by volume. The solution also contained 50 grams of stearic acid per liter.

Sample No. 10 was given a similar treatment, except that the stearic acid was omitted. The

loss or gain in strength was as follows:

S eari d t in t col s reng gs Solvent grams per liter- Warp Filling 8 Methanol 50 +9167}; 9 C. S. 3-28," TolllOL 5O 1% +18 10 "C. 8. 3-28," ToluoL 0 3)% +30 0 This comparison shows that when the C. S. 3-28", toluol solvent mixture is used there is no need to add an agent, such as stearic acid, to the solution, in order to protect the material against loss of strength. In each of the above cases, the loss of strength in the warp was negligible and there was a very substantial gain in strength in the filling. This is an interesting and remarkable result, as in the weighting process heretofore in current use, it is well known that there has gen-, erally been a substantial loss of strength, amounting frequently to as much as 30 to 40 per cent.

Attention is called to the brief time of immersion (14 seconds) of the fabric in the weighting bath in the foregoing experiments. When this is compared with the usual immersion of 30 to 40 minutes, characteristic of current practice, it will be seen that with the process of our invention the immersion equipment will be much less bulky, or conversely, a given equipment will have a much greater output, than in current practice.

Samples of knitted viscose and celanese rayon were given a generally similar treatment, except that they were passed through only one weighting cycle and received correspondingly less increase in weight. These were then subjected to the same series of tests with generally similar results. It was found that rayon can be weighted with antimony from a C. S. 3-28 solvent mixture, using the same procedure in immersion and fixation as in the above typical experiments and these samples afterward showed the same general characteristics as the sample of natural silk.

Silk and rayon fabric is notably more opaque when treated by our process, especially if antimony is used, than when weighted with tin by ordinary commercial processes.

Thus, by a combination of advantages all along the line our process results in substantial economics and at the same time notably improved results.

Although the examples given in detail are limited to antimony weighting, our process is applicable to tin; however, for reasons of cheapness we at present prefer antimony.

Our process is applicable to the'thread, yarn or woven fabric and to other textile materials besides these mentioned, such as cotton, wool, etc.

It will be obvious that the solvents mentioned above as good solvents for tin and antimony chloride are only a few of those available for the purpose; also that the list of commercial solvents given above is not complete but merely typical.

Although the only metals heretofore mentioned are tin and antimony, we do not wish to be limited to these metals. Many other metals are known to be more or less suitable for weighting purposes- Although the only salt heretofore mentioned is the chloride, we vdo not wish to be limited to this salt. Certain metals are best used in the form of their sulphates, nitrates, hydroxides, etc., depending upon the solubility of the salt in the particular solvent used.-

It has also been proposed to use mixtures of metallic salts or to use difierent salts in successive weighting cycles.

In general, almost any metallic salt or mixture of metallic salts which is fairly cheap and heavy and which is soluble in the type of solvent mixture characterizing our process and the metal of which can be fixed either by hydrolysis or by the phosphate, silicate or other treatment is suitable for our purpose and falls within the scope of our invention.

What we claim is:

1. The process of impregnating textile materials which comprises immersing the material in a solution of a weighting metal salt in a volatile organic solvent for said salt containing an unctuous constituent having the property of restraining the weakening action of said solution upon the fibres of the material, evaporating off the solvent and fixing the metal in the material.

2. The process of-impregnating textile materials which comprises immersing the material in a solution of a weighting metal salt in a volatile organic solvent for said salt containing a fatty acid, evaporating off the solvent and fixing the metalin the material.

3. The process of impregnating textile materials which comprises immersing the material in a solution of a weighting metal salt in an organic solvent mixture including a lower boiling solvent for said salt and a higher boiling constituent miscible therewith and having an oily component, evaporating off the solvent and fixing the metal in the material.

4. The process of impregnating textile material which comprises immersing the material in a solution of a weighting metal salt in an organic solvent mixture including a higher boiling mixed hydrocarbon of the parafiine series having an oily component and a lower boiling aromatic hydrocarbon solvent forsaid salt, evaporating off the solvent and fixing the metal in the material.

5. The process of impregnating textile material which comprises' immersing the material in a solution of a weighting metal salt in an organic 'a solution of a weighting metal salt in an organic solvent mixture including a mixed aliphatic hydrocarbon having an initial boiling'point of "approximately 320 degrees F. and an end point not higher than 410 F. and a solvent for said salt,

said solvent miscible with and having a lower boiling point than said hydrocarbon, evaporating oflE the solvent and fixing the metal in the material.

'7.The process of impregnating textile material which comprises immersing the material in a solution of a weighting metal salt in an organic solvent mixture including U. S. Commercial Standard 3-28 and toluol, evaporating ofl the solvent and fixing the metal in the material.

8. The process of impregnating textile material which comprises immersing the material in a solution of a weighting metal salt in a. volatile organic solvent for said salt having an oily component, acting to restrain the weakening action of said solution upon said material, evaporating off the solvent, immersing the material in an aqueous solution of sodium phosphate, washing and drying the material and immersing it in a solution of sodium silicate.

9. The process of impregnating textile materials which comprises immersing the material in a solution of a weighting metal salt in an organic solvent mixture including a solvent selected from the group consisting of ethylene dichloride, trichlor ethylene and chlorbenzol; and an aliphatic hydrocarbon selected from the group consisting of petroleum ether, solvent naphtha and U.- S. Commercial Standard 3-28.

10. The process of impregnating textile mate 

